The objective of this project is to investigate the processes that occur when a visually presented word is perceived. Two factors will be investigated: the processing of external visual information and the organization of the internal lexicon. These factors will be studied with two experimental paradigms: one incorporating a measure of perceptual accuracy and the other using a reaction time measure of the time to retrieve a word from the internal lexicon. The accuracy task will involve varying the subject's fixation position in tachistoscopic displays of words and nonwords. Preliminary evidence suggests that accuracy for words is higher than for nonwords at letter positions different from the fixation position, although there is no difference for the fixated letter itself. This may be due to an initial sampling of the stimulus at the fixation position, followed by further processing that spreads outward from fixation at a rate that depends on the degree of stimulus structure. The reaction time task will investigate the recognition of words containing affixes (e.g., DARKER) and attempt to distinguish between two possible hypotheses. On the one hand, these words may be recognized by decomposing them into base forms (DARK) and affixes (ER). On the other hand, they may be recognized as unitary wholes. The results of this study would have implications for the nature of functional units within words and for the organization of the internal lexicon.